Grinding machine



June 20, 1933.

w. J. GUILD 1?914,995

GRINDING MACHINE Filed April 21, 1930 s sheets-sheet 1 u E N @aw sw m l, 31 S s ."5 M1 3' lx\ I 5* o @D M\ e o l N\\\ e we lo Q O Q, u N 52 I m I wg f a ko I wald@ JI Guild,

June 20, 1933. w. J. GUILD 1,914,995

GRINDING MACHINE Filed April 2l, 1950 6 Sheets-Sheet 2 oB 15gg (IQlCLO GLLLLCL June 20, 1933G wl .'1. GUILD GRINDING MACHINE Filed April 2l, 1930 6 Sheets-Sheet `3 M@ I um c w Jur-1e 20, 1933 w. JGUILD 1,914,995

GRINDING MACIIIINE 'Filed April 21, 1930 6 Sheets-Sheet 4 mi@ e l ilily/I; l' 56 i i 3mm i 7 uwcld UTGLL'LICL June 20, 1933. w-J. GUILD 1,914,995'

GRINDING MACHINE Filed April 2l, 1930 6 Sheets-Sheet 5 Iyd 2m (aclo J' Guild www June 20, 1933.

w. J. GUILD 1,914,995

GRINDING MACHINE Filed yApril 2l, 1950 6 Sheets-Sheet 6 25o y 3mm Hy. 15-

(fnlcn Uf Guild PatentedV June 20, A17933 L UNITED STATES PATENT OFFICE wALno J. GUILD, or TlvoncEszrEaJ xAssAcHUsErTs, nss1eNon 'ro TEE 11min' MACHINE coHPANY, or WORCESTER, mssacnusn'r'rs, A CORPORATION or nassa- CHUSETTS GBIN'DING Application mea April 2i,

The invention relates particularly to grinding machines and Huid pressure mechanism for controlling them. The invention mvolves certain improvements upon prior machines as particularly pointed out in the specification.V

A particular object of the inventlon 1s to cause the extension of the normal reciprocaftory traverse between wheel 'and workpiece to dress and .true the grinding wheel without the use of somewhat complex mechanical instrulnentalities described in certain prior patents.

In other words, in this aspect thepresent 1n- -ventioninvolves a simplication of prior machines.

TheA invention makes use of a rotating gauge of the type disclosed in McDonou Reissue Patent No. 16,141. A particular o ject of the invention is to provide a simplified" control for holding such a rotating. gauge away from the workpiece during the preliminary grinding, allowing vit to engage with the workpiece during the taking aofthenal and finishing cuts thereon. To this end fluid pressure means is provided for controlling' the position of the gauge, and a valve device for controlling such means is provided, said ing placed in one position at tion it maintains until the actuation of the dressing diamond during a succeeding grind-V ing operation. The essential novel featureg in this mechanism consists inthe use ofthe pressure of the fluid that actuates the dressingdiamond and the pressure of the fluid that controls certain instrumentalities at the finish of a grinding operation, to actuate the valve that controls the position of the gauge.

One of the main objects of e .invention is to provide a pilot valve system of control for ithe jreciprocatory grinding carriage. Pilot valves to control main-valves, which in turn controlthe fiow of fluid to the opposite ends of a cylinder 'operating a carriage for a grinding machine, are by no means new, but

of Fig. 5.

the coordination of such, for the particular movements'necessary in this type of internal grinding machine involved new problems.

MACHINE p 1930. smal' No. 445,989.

Tothe solution of these the present invention isv particularly directed.

' The invention furtherinvolves improvements in instrumentalities for controlling the speed` with which the grinding carriage moves. It is desirable inthe machine f the class to which the invention is applied to cause the grinding carriage to move at one speed duringthe preliminary grinding, at a reduced speed for the final and finishing cuts, at a still 'different speed "for certain special operations such as dressing the wheel, and at a high speed for general movements such as separating the wheel and workpiece. It is also highl important that thespeed control devices-be adjustable.` The present invention involves improvements in mechanism of this type.

The invention further consist of a novel valve per se, and in certain com ination of. parts and motions, all of which will more fully appear from the following detailed description taken in connection with the accompanying drawings, in which j' Fig. -1 is a front elevation of a grinding machine constructed according to the inven tion. Y a Fig. 2 isa front elevation of'a certain casing located. on the front of the machine with the cover thereof removed, the parts' being` shown on an enlarged scale. y Fig. 3 is an enlarged fragmentary view of the dogs and stops carried by the grinding `carriage which cooperate with the mechanismv V85' shown in the upper part of Fig. 2.

Fig. 4 is a horizontal sectional view taken on the line 4-4 of Fig. 2.

Fig. 5 is a vertical sectional view on an enlarged scale of the main fluid pressure valve for thegrinding carriage, being takenon the line 5---5 of Fig. 9.

Fig. 6 is a front elevation of a certain casing contained in the inside of the machine, which elevation is taken on 'the line 6 of Fig. 4. 5

Fig. 7 is a sectional view on the line 7--7 Fig. 8 -isafvertical sectional viewona re'-l duced scale taken on theline 8.-8 of Fig. 5.

yso

the workhead 3.

Fig. 9 is a side elevation of part ofthe valve mechanism shown in Fig. 4.

f Fig. 10 is a. fragmentary side elevation of certain valve controlling mechanism on the rear of the machine.

f' Fig. 11 is a diagrammatic lView of the hydraulic or fluid pressure system.

Fig. 12 is a detailed vertical sectional view of a certain switch actuating mechanism.

Fig. 13 is a wiring diagram.

Like i'eference characters refer to like throughout the drawings.

Referring `to the drawings, particularly to Fig. 1, the machine provides the usual reciprocatory 'table or carriage 1, which nis ordinarily provided. in any internal grinding machine.r In such a machine either the grinding wheel or the work to be ground may be carried on the table 1, the reciprocation of the latter being utilized in eithercase to produce a relative traversing movement between the grinding wheel and the work. As hei'e shown, the table 1supports and carries a parts wheelhead 2 of the usual con'struction,-'while,

the work which is to be operated upon is held in a workhead 3, the latter being carried by a bridge 4, which spans the slideways provided by the machine frame for the back and forth movement of tle table l.

The normal cross or transverse feeding motion to causel the grinding wheel 5to produce successively deeper cuts on theworkpiece held in the chuck 6 is, in this embodiment of the invention, procured by moving To that end, the said Workhead 3 is mounted in guideways, not shown, provided by the bridge-V4 sothat it may be moved transverse t'o the direction of travel of the table-or carriage 1.` The actual mechanisni for producing this motion forms no part of the present invention, and niay'be of anyY suitable type, such as that disclosed in the `copending application No. 367,401, filed i May- 31, 1929, of. Guild and Burns, now

Patent No. 1,830,358, granted November 3,

1931, wherein ratchet and pawl means actuated by a piston and cylinder procure intermittent angular movement gf a screw shaft `7' which cooperates With a. nut element associated with the workhead-3 to produce the feeding increments. Desirably a hand wheel 8 is fastened to the shaft 7 for manual adjustment 'of the position of the Workhead 3.

The machine Aof the present invention, the same as that of the aforesaid Patent No. 1,830,358, utilizes a rotating gauge of the type invented by James G. McDonough and dis'- closed. in reissue Letters Patent No. 16,141, August 11, 1925, to bring the grinding operation. to a close.

Also in common with Patent No. 1,830,358, the machine provides yfor automatic dressing and truing of the grinding wheel, as disclosed in Patent No. 1,731,719 to j riage-jrl. See Figs.- 1 and 11. 'Fluid under Kempton and Gallimore. Likewise as in Patent No. 1,830,358, this automatic dressing is inaugurated by an electric contact-completed by mechanical instrumentalitie's actuated by the cross slide actuating means, substantially as disclosed in my former Patent No. 1,682,672, dated August 28, 1928. In order that the improvements of the present..

The grinding operation involves a large,

number of short reciprocatory movements of the carriage 1 in order to move the grinding wheel 5 back and forth within the hollow workpiece inthe'chuck 6, accompanied of course by rotation of said chuck and workpiece, and very rapid rotation of the'spindle 5a and grinding wheel 5. At one or both ends of the grinding stroke the shaft 7 is moved angularl by a slight amount, ,which causes the grin ing wheel 5 to cut deeper and deeper into the workpiece. the shaft 7 produces corresponding angular motion of a Wheel 9 attached to it (see Fig. 13) and a cam 10 ultimately comes in contact with an adjustable screw 11. This screw 11 is located in an arm 12 pivoted at 13 inside the cross feed box 14, and an ular movement of the arm 12 is adapted to c ose a circuit which procures the automatic dressing operation. Without describing the mechanism for this, which constitutes, in part, the subject matter of the present invention, it will be noted that in common with the aforesaid patents this dressing operation involves extensions of the normal reciprocatory working traverse of the table 1, and a simultaneous lowering of the dressing device or diamond 15, which is carried by an oscillatory member 16 suitably journalled in an adjustable base 17. The consequent movement of the grinding wheel 5 past the diamond 15 results in dressing of the rotating grinding Wheel, and the carriage 1 immediately returns said Wheel to the Workpiece. There the normal reciprocatory working traverse is resumed, and the -cross feed is continued, until a rotating gauge such as shown in the McDonough reissue patent referred to enters the bore in the workpiece. Entry of such gauge procures the closing of a circuit which causes the carriage 1 to -travel outwardly, this time without any lowering of the/diamond 15 into the path of the grinding wheel 5, the carriage being ultimately brought to a stop substantially in the position shown in Fig. 1. v

v In common with the machine of the aforementioned patents, tliepresent machineprovides a cylinder l18 which desirably is attachedv to the base of the machine, this cyl- .inder containing a piston, not illustrated, whose ,piston rod 19 is connected to the earpressure is admitted alternately to opposite ends of the cylinder 18, by means of pipes 20 Such angular motion of and 21, Fig. 11, and in thisOmanner the reciprocatory traverse of the carriage 1 is procured. l' y l The normal reciprocatory traverse to procure the working reciprocation between grinding wheel and workpiece, is procured, as in the aforementioned patents, by dogs or stops 22 and 23,' carried'by the carriage 1, Whlch alternately engage the upwardly extending arms 25 and 26 of a -reversing mem- Y ber 24.. However, the construction and mode i of. operation of the fluid pressure system which ultimately causes fluid to flow through l the pipes 20 and 21 responsive to shifting of the reversing member 24 is, according to the A present invention, quite different fromthe fluid pressure system described in theafore.-

said patents. The present invention also involves a. decided simplification of the stops and dogs and like actuating mechanism carriedby the table 1 in order to control the amplified or extended movement of said table, both to dress and true the grinding andthe other to exhaust.

wheel, and to bring'the carriage 1 to its position of rest, as shown in Fig. 1. l

The fluid pressure actuating and reversing mechanism of the present invention involves the use of .a pilot valvewhich is actuated by the reversing member. 24, said pilot valve in turn controlling a main valve which connects the pipes 20 and 21, one to pressure Referring now to Figs. 2, 4 and 11, the pilot valve27 is located in a suitable casing 28 which is in turn attached to a large or general casing 29 suitably attached to the machine base, the front of which may be plainly seen in Fig. 1. The pilot' valve casing 28 the casing 28, and which are spaced apart by reduced portions 37 andv 38. At one end of the valve member 27 there is a further rcduccd portion 39, bounded on the end 'by a full diameter portion 40. A forked'portion 41 of the reversing member 24 surrounds the reduced portion 39, and the width of the fork and length ot the reduced portion is such` that when thc reversing member is moved from one extreme position to the other, the valve 27 is not moved until said reversing member passes its central position.

Associated with the reversing member 24 is any convenienttorm of thel usual snap-over device, the actuating member. 42`0 f which operates a wedge member 43 fastened to the reversing member 24. L

` The valve casing 28 provides a. pair of ports 44-and 45 which lead fluid to the'opposite ends of the main valve, and an exhaustl or discharge port 46. Y When iiuid is admitted to the port 45, which is the right hand port of the pilot valve 27, 28, it'fiows through -a conduit 47 which leads to the right hand ,end of the main valve, which will cause lthe main valve to be positioned to drive the carriage 1 to the right, Fig. 1. W'hen fluid is admitted to the port 44 of the pilot valve, however, the fluid flows through a pair of conduits 48 and 49 to the left hand end of the main reversing valve. During the y"normal operation of the `machine the conduits 48 land 49 are always in communication, bc-

ing connected through a valve whose casing is numbered 50. `Under what conditions the connections between the conduits 48 and 49 is broken will be hereinafter pointed out.

The main valve'casing 51, which may be attached to the rcar ofthe box 29 as shown in the sectional view of Fig. 4, is illustrated in that figure, and is shown in front elevation in Fig. 6. vA right hand elevation of it is shown in Fig. l'9, and 'a vertical sectional view of itis shown in Fig. 5. Referring now to Figs, 4 and 5 for the actual structure, and to Fig. 11 for an easy understanding of the functional operation of the valve, it will be seen that the conduit 47 connects to a cylinder bore 52, while the conduit 49 connects to a similar bore 53. In these bores 52 and 53 'are located pistons or fplungers 54 and 55 whose ends abut plugs or the like 56 and 57 in the ends of the main valve member designated generally by the numeral 58.

` As shown in Figs. 4, 5 and 11, the Amain valve 58 comprises a hollow cylindrical member, the ends of which are closed off by the plugs 56 and 57 aforesaid, a divisional wall 59 being left in between these plugs thus dividing'the interior of the valve into two chambers. The valve member 58 fits slidably in a bore 60 provided by the casing 51, and-is'adapted to be'urged into either of its end positions as the fluid' from the pilot valve vis alternately admitted to the chambers 52 and 53.v The left hand chamber of the valve Y member 58 is numbered 61 and the right hand chamber is numbered 62.V The chamber 61 provides two sets,of ports through the side wall of the valve, 63 and 64. The chamber 62 provides `three sets of ports l through its-'side wall, 65, 66 and 67. These five ports 63, 64, 65,466 and 67 control the` vadmission of fluid from the main supply source 33 to th conduits 20 and 2 1 leading to the opposite ends of'the cylinder 18 in order to move the carriage 1;-at any given time one of said conduits'20 and 2 1 being connected to the'pressure, and the other of said conduits being connectedto an exhaust or/discharge port 68, excepting only when the table is held at the idle position by a stop valve which will be described. Before describing the ports with which the aforesaid ports cooperate, the manner in which fluid is introduced into the valve casing 51 will be descri-bed.

The main liuid supply line 32 connects at 69 to a chamber 70 in which is contained a rotatable valve 71 which normally, however, offers free passage through a port-72 for the pressure fluid. lort 72 connects with the passage 73 in which is located a throttle valve 74 which may be manually controlled from the front of the machine by means of a knob 75. The other side of the throttle valve 74 connects to a cross passage 76 which connects with passages 77 and 78. Passage 77 terminates in a port 79 and the passage 78 terminates in the port 80. v

When the main valve 58 is in its left hand position as shown in all figures, the port 79 is in communimation with the port 63, thus admitting fluid to the chamber 61.. At that time also the port 64 through the valve 58 is in communication with a port 81 at the end of the conduit 20,so that fluid is admitted to the left hand end of fthe cylinder 18. At that time also the por't 65 of the valve member 58 is in communication with the exhaust port 68, While the chamber 62 receives the fluid from the right hand end of the cylinder 18 for exhaust, through a port 82 that is at i that time in communication With the port 66 of the valve member. The port 82 is not at the end of the conduit 21, but communicates with a chamber 83.in which is locateda/"rotatable valve 84 which normally allows fluid tol flow through a port 85 that communicates with a passage 86 Which is directly connected Vto the end of the conduit 21. 'A cross passage 87 connects the passage 86 with a port 88 for a purpose which will hereinafter appear. e

When the valve member 58 is moved to the right hand' position, the port 63'is moved away from the port v79, and fluid can therefore no longer fiow to the left hand end of the `cylinder 18, said left hand end being onl the contrary connected to the exhaust port 68.

l This connect-ion is effected by reason of the fact that the port 63 now is in communication with the port 8l, while the port 64 is in 'comn'iunication With the port 68. At the same time fluid is admittedto the righthand end of the cylinder 18 by reason of the fact that the port 66 is `in communie. tion with the port 8O at the end o f the passage 78, thus admitting fluid to the cli-amber 62.V The inside of the chamber 62 is at that time completely cut ofi' from the exhaust port 68, but the'ports Iv and 67 are in communication respectively with ports 82 and 88, and so two passages are provided for the flowV of fluidto the conduit'v ing wheel 5 to Aenter the chuck 6, and to place the reversing dogs 22 and 23 on either side of the reversing member 24 and projections 25 'and 26, the carriage 1 will be reciprocated back and forth, as said reversing member 24 is mechanically shifted first to one side and then the other, because of the fact that the pilot valve'27 is shifted back and forth, thus admitting fluid to the chambers 52 and 53 and therefore alternately moving the main valve member 58 from one extreme position to the other, to admit the fluid through the passages described first to the right and then to the left hand side of the operating cylinder 18. The use of the pilot valve 27 to operate the mam Valve permits a small balanced valve to'be operated by the mechanical means responsive to the movement of the carriage 1, and thus to obtain a quick action of said pilot valve, which in turn proeures fluid pressure actuation of a larger' valve that will handle the full volume supply of pressure to move they carriage 1. The use of the fluid pressure system vherein described also permits the amplification of the traverse of the carriage 1 for l wheel dressing purposes to be obtained with avery simple mechanical mechanism in place of the rathercomplicated mechanical devices shown in the aforesaid patents. The manner and mode of operation of this part of the present invention will now be set forth.

Once the carriagel is started reciprocating in Working position, it continues its rcciprocation with continual small angular movementof the cross feeding Wheel 8 and screw shaft 7 until such time as the cam member 10 on the Wheel 9, which is also fastened to the shaft 7 (see Fig. 13) comes into contact with the aforesaid screw 11 and so rocks the lever arm 12. Such movement of the arm 12 brings a contact member 89 carried by the arm into engagement with a contact 90 on a suitably mounted and insulated arm 91. r1`he arm 12 is grounded, as illustrated at 92, while the contact 90 is connected by a conductor 93 to one terminal 94 of a switch which is designated as a Whole by the numeral 95, and Whose oscillatory switch member 96 at `that time connects the terminal 94 with a terminal 97, a connector 97 providing an electrical connection from Ythe terminal 94 to the end of switch member 96. The terminal 97 is connected by. a conductor 98 to one terminal procures the dressin operation in a manner that will now be set` orth.

The magnet 99 is located in the casing 29 on the front of the machine, and has associated therewith an armature 102 which is attached l ,to a lever 103, the bottom end of 'which is connected at 104 to a valve member 105, and the upper end of which provides an inclined projecting surface 106 for a purpose which t will hereinafter appear. Energization of the magnet 99 draws the arm'103 in a c ounterclockwise direction to move the valve member 105 to the right.

The valve member 105 is located in the casing 50, and-said valve member and said casing really operate as two separate valves. Thus the movement to the Iright of the valve member 105 performs two functions, namely, it causes the movement-down into dressing position of the diamond 15, 'and it actsJ to prevent normal reversal of the 'carriage 1 at the right hand end of its normal reciprocatory workingttstroke. y

Referring now particularly to Figs. 4 and 11, the valve member 105 is generally cylindrical'and ,fits with a sliding fit in the cylindrical bore in thecasing 50. It provides two portions of reduced diameter 107 and 108, and it also provides a longitudinal bore 109 which is piercedby apair of transversebores 110 and 111. The bore 109 is blocked at the end from whichit is drilled by a plug v 112, and does not .extend beyond the left hand transverse bore 110.

The casing provides five ports owhich are, reading from left to right, ports 113,-

114, 115, 116,'and 117. During the normal operation of the grinding machine, while the carriage 1 is being reciprocated as hereinbefore described, the reduced portion- 108 of the valve member 105 connects the .ports 116 'and 117, the former being the terminus of the'fconduit 49 at one end, and the'` latter being the terminus of the conduit48 at one end. It is thusthat iuid normally flows from the pilot valve 27 28 to the main valve 58,. When, however, the valve member 105 is-shifted to the right as just described, the ports 116 and117 are no longer in communication';-the transverse bore 111 is placed in line with the port 116, and the transverse bore 110, is placed in line with the -port 113, which latter port is-an A'exhaust port, so that v the conduit 49 is connected to the exhaust and thus the bore 53 is connected to exhaust and 'the piston 55 can be moved to the left.

It therefore follows thatat the end of the ,Y le'ftvvaid movement of the carriagel' (providing the carriage\is so moving when the vvalve -105 was shifted), the reversing lever 24 will be shifted as usual, and ,the pilot valve 27 will ybe moved, and this lwill cause fluid to be admitted to shift the -main valve 58 to the left, causing the carriage 1 to bel 'j withdrawn tothe right,'but the subsequent grinding wheel out of the workpiece, where it will beultimately reversed as will be hereinafter described.

The other Ifunction of the valve 50,105', is to cause the diamond 15 to be lowered into the path of the wheel ,5. In the position of parts shown in Figs. 4 and 111, the port 114 is connected to the port 113 and disconnected from the port 11-5. The port 11'5 is connected by means of one or more conduits 118, 119 with the source ofpressure such as the pump 33. The port 114 is connected by aconduit 120 with a cylinder 121 in which is located'a piston 122. Movement ofthe valve member 105't0 the right, connects together the ports 114 and 115, so as to admit Huid through the pipe 1-20 to the cylinder 121. This cylinder 121 is` located in the base 17 for the diamond oscillatory member 16, and admission of Huid to it causes downward movement of the dressing device by reason of oscillation of the member 16. The manner in which this takes place responsive'to movement. of the piston 122 forms no part of the present invention, since the mechanism for moving the diamond is the invention of .HealdV and Guild and described in application Serial No. 25,900 now Patent No. 1,77 9,094, granted October'v 21, 1930, while the specific mounting forthe oscillatory member 16and the various parts associated with it are fully described in Patent No.'1,655,903 grantedl to Guild and Grimshaw on January 10, 1928.

The movement `of the diamond 15 into position and the withdrawal of the grinding whe l 5 from the workpiece causes contact between the wheel and dressing^ device-with consequent truing of the former. The movement of the carriage 1 tothe right takes place at a slow rate of speed since the valve member 71 is moved to restrict the flow of the Huid v to a shaft 125. This shaft 125 extends along the lback of the machine and forms -the p iv-` otal mounting for the actuating mechanism forthe diamond. i On one. .end of rt is fastened an arin 126, Fig. 10. The end ofthe arm 126 has pivotally attached thereto a threaded rod-127 havin two pairs of nuts 128 and 129 thereon. etween the double pair of nuts 128 and 129 is a lug 130 through which the threaded rod passes. Upward movement of the rod 127 raises the lug 130, and as the lug 130 is formed on an arm.13l which is attached atA 132 to a bell crank lever 133, it causes counterclockwise oscilla- ,tion of the said bell crank lever 133. The bell crank lever 133 is connected by a link 134 to a lever 135 which is fastened to the'shaft 136 of the slow-down valve 71. It will thus' be seen that rocking ofthe shaft-125 causes oscillation of the slow-down valve 71, and

consequently whenever the diamond 15 is- `of the action of mechanical means described in the aforesaid patent to Heald and Guild.

This repositioning of the shaft 125 causes vresetting of the valve 71, more or less, in

accordance with the setting of the nuts 128,

- as will be readily apparent from Fig. 10.

It will .be recollected that on the right yhandmovement of the carriage 1, the reversng ever 24 iwas shifted as usual by the engagement of the table dog 22 with its projection 26. The mounting of the lever` 24 provides for suicient movement so thatv the dog 22 may ride beyond it, which it does durin the dressing ofthe grinding wheel descri d. The pilot valvel 27 is, therefore, in position to cause the carriage 1 to return the grinding wheel 5 to the work, except thato it is inoperative to do so owing to the shifting of the valve 105. Consequently re-A shifting of the valve 105 into its original position, will case the return of the carnage. This is effected in the following manner.

Referring to Fig. 3, the carriage 1 provides a carrying block 137 wh1ch, the same as the carrying blocks 138 and 139 for the dogs 22 and 23, is adjustably mounted on the front of said carriage. striking dog 140 is attached to said carrying block, andl .of a vrotating gauge according to the Mcin the path of travel of this dog 140 is the projecting portion 106 of the lever 103. Conuently it will be Seen thatr movement to I the right of the carriage 1 will cause engagement of the dog 140 with the portion 106 of the lever 103, and this will forcibly reposition this lever and therefore also the valve member 105.v Prior to this time, the magnet 99 is deenergized, so as to let the valve 105 remain repositioned, and this deenergization of the magnet 99 is accomplished 'in the following manner. A

- The switch member whose oscillatory` movement of the carriage 1, a dog or stop i 150 carried by the carrying block 139 strikes the arm 141, the right hand button'146 is depressed; and this snaps the switch member 96 to open position. This placing of the switch 95 in off-position occurs just prior to the actuation bythe dog 140 of the lever 103, and consequently there is no force opposing repositioning of the valve 105.

As` soon as -theportion 108 reestablishes the connection between the ports 116 and 117, the main valve 58 will be shifted and the carriage 1 will be reversed. In order to shift the valve completely to its original position, and in order to uicken the action of the mechanicall means ]ust described, the following fluid vpressure connections are established to create a positive force holding the valve member 105 in its normal position.

Referring no w to Figs. 4 and 11,'the port 116 has shunted into it a passage 151 which I connects with a bore 152 in which is located a small piston-153. The small piston 153 is'an integral part of the plug 112, and, consequently the least opening of the port 116` will admitluid tothe bore 152 and cause the pist-on ,153 to be urged to the left, thusl positively assisting in the return of the valve member'105. It will be understood that shifting of the valve 105 vreconnects the port 113 'with the port 114, and so opens the conduit 120to exhaust, allowing the Huid to be pressed out of the cylinder 121 when the mechanical means operates to reposition the diamond..`

This mechanical means is described in the patent to Heald and Guild and operates as the carriage 1 returns the wheel 5 to grinding position.

,It has already lbeen mentioned that the A machine of the present invention makes use somewhat as shown in Patent N o.` 1,534,302

to Prentice Conradson and others, granted April 21, 1925. It has been found very-desirable, hoxveyer, that the gau should not con# tact with the workpiece uring all of the grinding operation, since repeated shocksv are apt to cause some misalinement in the chuck or other damage. In the above noted Patent No. 1,830,358, one manner of holding the gauge out of position and away from the workpiece until the workpiece 'is almost brought lto correct size is shown and described. The present invention involves an improvement in the apparatus therein set forth, in the particular means for allowing the gauge .to operate, and for holding it inoperative during the preliminary' grinding. Referring now to'Fig.- 1, at the left hand end of the workhead 3 is a casing 155, which d contains a cylinder 156 having apiston 157 thereon. The piston has'a piston rod which is located just in front of 'a member 158 which is attached to the'gauge rod 159. A

U inder 156, the gauge rod is shifted to the left and held there so as to prevent the gauge from gauging the workpiece.

During' the preliminary grinding, the iuid is admitted to the cylinder 156, passing by way of the supply conduit 119 and a branchv conduit 163 to a port 164 in a valve casing 165. `The port 164 is at that time in communication with a Vport 166 leading to a conduit 167 thatv connects ,to the cylinder 156. In the valve casing 165 is a valve mem- -ber168 comprising a pair of full diameter portions, connected by a reduced portion 169.

During the preliminary grinding operation, Ithe reduced portion 169 allows communication between the ports 164 and 166 as aforesaid, whilegone of the full diameter portions blocks olf the exhaust portv 17 0.

A conduit 171 is shunted intovthe conduit 120 and thisl connects the conduit 120 with a 1" port 172 in the end ofthe valve casing 165.

When fluid is admitted into the port 172 and valve casing 165, the valve member 168 is urged to the left, and the fiuid supply port 164 is shut olf, while the port.166 leading tothe cylinderA 156 is connected by way of the reduced portion 169 with sage 17 0. Y Thus it will be seen that energization of the magnet 99 and consequent shift- :inv of the valve member 105,- allowing uid 5' to flow through the conduit 120, also shifts the valve 168 andallows fluidto exhaust from the cylinder/156, thus permitting the gauge 'on the gauge rod 159 thereafter to .engagefthe workpiece undert e influence of the spring 160, the gauge being urged out of engagement at each left hand movement of thecarriage 1 as described in the patent to Conradson aforesaid.

After the/dressing operation and the reentry ofthe grinding wheel 5 into the work- .these two valves.

the exh'ailst paspiece :is-described', the carriage 1 continues its llmitedreclprocatory traverse over the same working range as during the preliminary lgrinding operation, which is determined by the setting ofthe adjustable blocks 138 and 139 that carrythe table dogs 22 and 23. The rate of movement of the carriage, however, is determined by the setting of' the valves 71 kand 74, the carriage .reciprocating with a speed 'determined b the more restricted of )rdinarily thisl would be the valve 71, whose position during the final and finishing` cuts taken on the workpieceis .'determined by the setting of the adjustable nuts 128 shown inFig. '10.

, During this time the gauge, not shown, which is continually rotating at the same speed as the workpiece, as set forth inthe patents to McDonough and Conradson and which is intermittently urged against the workpiece as also set forth in those patents, is continually endeavoring to enter the bore of the workpiece. Such entry occurs, however, only when the workpiece reaches the ultimate finished diameter.. When that occurs the gauge rod 159 undergoes a greater movement to the right than heretofore, and

this action brings together two contact terminals 173 and 1,74, the former of whicheis grounded, and the latter of which isconnected by a conductor 175 to an electromagnet 176. The other terminal of the electromagnet 176 is connected by a shunt lead 177 to the conductor 100 comingfrom the generator G, and thus at that time the electromagnet 176 is energized.,

The electromagnet 176 is illustrated only in 13, but it is-located directly behind the electromagnet 99 and has associated therewith an'armature member 178 on a. lever 17 9, which is pivotally mounted 1on the same pivot 180 that holds the (liever 103. Likewise it has a portion 181 exten ing upwardly from the casing 29,' and indeed all these parts are duplicatesof the armature lever etc. associated with themagnet 99. Y Y

The upper end 181 of the lever 179 vis directly in the path of travel of the left hand shown in Fig. 3, but capable of being lifted up beyond .saidposition Raising of the end 181 movement of the carriage lrthe dog 22 is4 lifted entirely clear of the portion 26 of the reversing lever 24. The pilot valve 27 is therefore not shifted to the left, and the carriage 1 continues outwardly, carrying the of the lever 17 9 lifts the dog 22 (it will be. i

grinding wheel to idle position where it is stopped in the following manner It will be remembered that on the right hand stroke of the carriage 1, the fluid from the right hand end of the cylinder 18 passes through a valve 83. 4This valve 83 has a stem 18 to which is fastened an` arm 184 y(Fig. 9).

' A spring 185 .attached to the armf'a-nd to a Val() 18. It will be apparent that' thereafter the carriage can move no further to the right. It should be noted, however, that whenever the pilot valve 27 is moved to move the main valve 58 to its right hand position, fluid can pass to the right hand end of the cylinder 18 by way of the passage 87 and ports 67 and 88.

Movement of the lever 179 also operates a l,

valve and causes the grinding wheel to move laterally away from the workpiece before it is removed therefrom axially, causes a resetting of the speed controlvalve 71 to its wide open position, and causesthe gauge to be held hack in its inoperative position. To that end the lever 179 is operatively connected at 187 to a valve member 188 which is located in a casing 189 which may be desirably formed integrally with the casing 29. The valve member 188 provides a single reduced portion 190 which is adapted to connect a port 191 either with a pressure suppl port v 192 or with an exhaust port 193. fore movementto the right of the valve member 188 responsive to the energization of the magnet 176, this valve member 188 connects together `the ports 191 and 193, so that any fluid in conduit 194 is connected to exhaust.

` The movement of the valve member 188 to the right, however, closes the exhaust port 193 and opens the fluid entrance port .192 (which connects to the supply conduit 119) so as to admit the pressure fluid to the conduit `194.

This conduit 194 leads to a cylinder 195 in vwhich is a piston l196 that causes lateralv separation of the wheel and workpiece. The rest ofthe mechanism for performing this xoperation, however, forms no part of the present invention, and may be of any desired form and is set forth in previous patents so ihat it will not be herein described.

Fluid from the conduit'194 also enters a cylinder .197 having a piston 198. Referring now to Fig. 10, this piston and cylinder` are herein shown, andthe piston is in engagement with one end of the lever arm 135. Outward movement of the pist-ou therefore .moves the lever arm and the valvel 71 .in a clockwise direction, Fig. 10, and completely resets this with the roughing cuts at a speed determined solely by the manually adjusted valve 7 4.

The conduit 194 also connects to the cylinder 165, at the left hand end thereof, Fig. 11, and consequently repositions .the valve 168 in its right hand position, allowing pressure fluid to flow into the cylinder 156and to maintain the gauge away from the workpiece during the first part of the next grindin g operation. l

Movement of the carriage 1 to idle position is desirably at a high rate of speed irrespective of the setting of the valve 74, and thls is provided for in the following manner i On the back of the carriage 1 is a track cam member 200 which cooperates with a short arm 201 having a roller 202 that fits in the track of the cam, the arln being fastened to a shaft 203. Movementof this arm may operate the draw rod to open and vclose the chuck 6,.and/or turn on and off the water supply for the grinding operation. At all events,a valve 204, Fig. 11, is formed on the shaft 203, and this valve is located in a fluid supply line 205.v When the carriage 1 starts outwardly, it goes at slow speed during the first part of its movement until the cam 200 has moved its arm 201 and the valve 204, whereupon fluid is dmitted to a conduit 206 leading to a chamber 207 in the casing51. A piston or plunger 208 is located in this vchamber or bore and is normally shown in the position in Fi'f. 11 by reason of the pressure of a spring 209. The plunger 208 has a reduced portion 210, which. when the plunger is moved upwardly permits fluid to flow along a passage 211 which connects to the chamber at one end' and to a cross passage 212 at the other end. The cross passage 212 `leads by way of a valve 213 to the passage 76, and thus when the plunger 208 is raised, fluid can enter this passage independently of theffvalve 74, and so the carriage 1 will be moved at a speed determined only by the setting of the valve 213.

The conduit 206 alsoconnects to a shunt conduit 215 which leads to a cylinder 216 having a piston 217 that operates a clutch in the workhead to stop rotation of the chuck 6. The mechanical features of this mechanism, however, do not concern the present invention 4and will not be described. An exhaust port 218 is provided in the valve casing 219 for the valve 204, so that when the valve is replaced as Ait will be by the cam 200 as the grinding wheel 5 enters a new workpiece, the chamber 207 will be connected to exhaust ahd-thus the passage 211 will be blocked in order to compel the fluid to pass in series through the valves 71 and 74.

From the foregoing description it will be seen that each grin operation is determined by the entry o the gauge into the bore' of the workpiece. Since, however, the' Egauge 'is not allowed to operate until the dressing operation takes place, and since thedressing diamond 15 must have a certain definite relationship'to the grinding wheel in order to true it during each dressing opwhich normally occurs between grinding p wheel and workpiece, together with a slight added increment to secure actual removal of material from the wheel 5, in order to true its surface and render it sharp and free cut-v ting. To that end the wheelhead 2 is mounted upon a cross slide 2a which is adapted to be moved laterally of .the machine frame by means of a screw shaft 220. Every time the carriage 1 runs out to rest position a cam;

member 221, carried on a stationary part of the machine is engaged by a roller 222, fastened toa pivotally mounted member 223 upon which is also mounted a pawl 224 consequent elevation of the pawl 224 actuates a ratchet 225 attached'directly or indirectly to the screw shaft 220, and thus causes movement of the wheelhead 2, this action being termed compensating for wheel wear fand dressing. This particular mechanism is not per se subject to the present invention being illustrated in the aforesaid Patent No. 1,830,358.

' The grinding machine ofthe present invention is intended to operate automatically from the time that the workpiece is placed in the chuck 6 until it is removed therefrom and another workpiece substituted in its stead. Nevertheless, the carriage 1 hasto`be manually started to commence the grinding operation, and it is also` desirable that the machine have manual controls in order that one or two' workpieces may-be groundnon-automaticallowered and the carriage 1 to withdraw the grinding wheel from the workpiece, such means constituting simply a conductor 226 shunted .into the conductor 98 and connected to'a push button switch 227, one terminal of which is grounded at 228. Similarly/also, a push button switch 229 is adapted at any time to energize the electromagnet 17 6l to` cause the carriage 1 to run out to idle position, one

Y terminal of this switch\ 229 being connected to a conductor 230 that connects to the lead -17 5, and the other terminal being connected done without touching the arm 141', a knob to ground 228.' A shaft 231, having a lever 232 on theI front of the machine, is rotatably mounted in the general casing and provides an eccentric pin which-fits in a slot 233 providedby the reversing member 24, and thus the reversing member 24 may be manually operated at any time.

The switch 95 vmust be susceptible of manual operation and in order that this may be 234 is provided on the front of the machine on the end of a shaft 235. On the'shaft 235v is a block 236 having a pairof pins 237 which fit underneath the projecting portions 143 and 144 to oscillate the. member 141 on its ivot 142, and thus to actuate the push buttons 145 or 146. Also the shafts for the valves 74 and 213 project through the front of the casing 29 and terminate 1n dial members 75 and 240 respectively. -By turning the dial 240,` the valve 213 can be entirely shut oif so as to prevent the carriage from travelling at its highest rate of speed, or at least limiting it to the speed determined by the valves 74 and 71. Y j

It should 'be noted that the' valve 58 will shift rapidly under the impulses given it by the small pistons 54 and 55, because the valve is hollow, and thereforeA has little inertia. Notwithstanding this, the valve 58 controlsa largenumber of ports, and `is perfectly balanced both radially1 and. axially. The ends of the main bore A60 desirably provide vent holes (not shown) so` that neither air nor escaping iiuid (oil) will impede the movement of the valve member 58. These vent holes may be -connected by a pipe to each other orto the sump provided by machines lof this character Afor the pressure fluid.

The operation of the machine has been largely indicated in Ithe'foregoing description of the various parts and mechanisms, but in the interest of a thorough understanding of .the invention it will be briefly re` viewed. Assuming a workpiece is placed in the chuck 6, and alladjustments made, with the carriage 1 in the position shown in Fig.- 1, the grinding operation wllbe started by shifting the lever 232 to the left thus disposing the reversing member 24 in its right hand position, and placingrthe pilot valve its lefthand position. his causes iiuid to pass f through the valve member 105, which at that time is in the position shown in Fig. 11, the iuid being admitted to the left hand end of the main valve member 58, thus disposing. said valve member in its right hand positionW and causin fluid tdbe admitted to the right hand end o the cylinder 18. The carriage 1 thereupon moves to the left carrying the grinding Vwheel into' the workpiece, the left handpivotally mounted dog22 over the right hand prong 26 of' the reversing lever 24- as it'does so.

Thecarrlage 'continuesjto reciprocatepback 13? supply of fluid to the gauge controlling cylreason of cross feed mechanism not described herein, the reciprocatory motion being effected by alternate shifting of the pilot valve 27 and consequent movement of the main valve member 58.l

When the work by grinding has reached a certain predetermined diameter, which is desirably just short of finished'size, the cam 10 which is connectedto the cross feed screw shaft 7 engages the adjustable screw 11 and brings Itogether contacts 89 and 90. The switch member 96 is at this time in the position shown in Fig. 12 where it connects the terminal 94 to terminal 97'. During the aforesaid passage of the carriage 1 from its inoperative position, to begin its grinding reciprocation, it caused engagement of the switch dog 150 with the arm 141 and necessarily depressed the left hand button 145 of the switch 95. In passing it should be noted that the mechanism of the switch is not illustrated, as it would have to be shown on a very enlarged scale, and the switch is of a very common type and no part of the present invention.

The bringing together of the contacts 89 and 90 with the switch member 96 in the position shown in Fig. 12 closes the circuit which energizes the magnet 99. This, as already described, causes the attraction of an armature 102, the shifting to the right of valve member 105, and the raising/of the projection 106. By this action, fluid pressure being prevented from reaching the left hand side of the main valvev 58, the ultimate travel to the right of the carriage 1 is assured, at the same time fluid is directly admitted to the cylinder 121 and the diamond 15 is lowered as soon as it is permitted to do so by mechanical controlling instrumentalities which are the subject matter of the patent to Heald and Guild already referred to. At the same time admission of the fluid to the pipe 120 leading to the diamond operating cylinder 121 causes the fluid to flow into the right hand end of the cylinder 165, thus causing shifting of the valve member 168 therein and cutting off the inder 156, Previously to this time thel gauge had been maintained by the piston 157 in said cylinder out of the range of thegrinding ywheel and workpiece. By the cutting off of the pressure from the cylinder 156, however, the gauge operating spring 160 is allowed to shift the gauge `rod 159 to the right and thereafter, for the remainder f the grir'ling operation, the gauge engages the -workiece at each stroke of the carriage 1, being urged against the workpiece by 'the spring 160, and being removed away from the workpiece at each left hand stroke of the grinding wheel 5 in order thatthegrinding Wheel may `completely grind the workpiece by the engagement of the left hand end of the carriage 1 with the adjustable bolt 161. l

. explained by reference to the aforesaid 'patent to Heald and Guild. This procures, through the connections described'and shown in Fig. 10, an angular displacement, more or less, of the valve 71, thus slowing down the speed of travel of the carriage 1 for the dressing operation.

The outward travel of the carriage does not fail to shift the pilot valve 27 to its left hand position by reason of engagement of the table dog 22 with the right hand prong 26 of the reversing lever 24. This is ineffective, however, at first to stop the travel of the carriage by reason of the shifting of the valve 105, as fully described. Ultimate reshifting of the valve 105 to its original position by engagement of the dog 140 with the projection 106, however, causes immediate shifting of the main valve 58 and return of the grinding wheel to the workpiece. turn motion, the dog 150 strikes the arm 141 and causes shifting of the switch member 96, so that the magnet 99 is deenergized despite maintenance of tbe engagement between contacts 89 and 90.

The reshifting of the valve 105 to its original position also `cuts off the fluid pressure to the diamond operating cylinder 121 and the diamond is raised again by mechanical means associated with the carriage 1 and described` in the Heald and Guild patent. Such repositioning of the diamond 15 involves movement of the shaft 125 and disrepositions the valve 71, more or less, according to the setting of the nuts 128. Thus the grinding operation is resumed at any speed or traverse from the original grinding speed as ,determined by the adjustment of the valve )74,to the reduced speed or traverse for the dressing operation as determined bythe original shifting of the valve 71, both inclusive. It will be noted that the opening 0f the supply pipe 120 to the exhaust to allow repositioning of the diamond, while it relieves thepressure against lthe right hand end of valve member 168, does not change the position of that valve member, because there is at that timeno force to move it to the right.

Th'e grinding wheel now takes the final and Afinishing cuts upon the workpiece, re .ciproca'ting back and forth vuntil the Workpiece borecomes to the desired sizeand the gauge enters therein. When that happens, the gauge rod 159 moves and brings to- Just before this regether contacts 173and 174. This enerfgtizes the magnet 176, with the consequent liing of the projection 181, which projection raises the left hand dog 22 high enough to cause it to clear the right hand prong 26 of the reversing lever 24. The carriage 1, therefore, continues to move to the right carrying the grinding wheel out 'of the workpiece, thus deinitely terminating the grinding opera.-l

tion.

The energization of the magnet 176, also shifts the valve member 188 to the right and causes the actuation of severalother instrumentalities. In the first place` iluid is admitted tothe cylinder 195 which actuates .the piston 196'to cause the wheel `to move laterally away from the workpiece beforev it has entirely left the bore thereof in order to prevent scratch marks being formed on the surface of the workpiece This mechanism is not per se part of the present invention and is not described herein, but the same conduit 194 which leads fluid pressure to this back-0H cylinder may be used for other purposes, as described.

Connected to the pipe 194 is the left hand end ofthe cylinder 165 and also the cylinder 197. The latter completely resets' the automatically operated slow-down valve 71 to its wide-open position when fluid is admitted to it. Admission of fluid to the former reshifts the valve member 168 to its right hand posicauses fluid to be admitted through pipe 206v to chamber 207 thus raising the plunger208 and admitting fluid through the by-pass pas,-

- sage 211 so that the travel to either positioi of the carriagewill'take place at a speed which is controlled only. y the settingnof the valve 2 13 by the knob 240. The al occurrence 1n a cycle of grinding involves the engagement of some portion of the carriage with the arm 184,.-thus turning -the valve member 84 andpreventing fluid from escaping from the right hand end ofthe cylinder 18. This stops the .carriage 1 but, as will be remembered, does not prevent the carriage from being. startediagain by shifting of the hand lever232,` since an ultimate passage is provided for the iiuid when the main valve-58 is moved toits right hand position.

`Although the invention has been described Ain considerable detail, it will beevident that various modifications may be madeA within following claims.-

I claim:

` 1. In a grinding machine, a table or carriage reciprocation of which causes relative traverse between grinding wheel'and workpiece, fluid pressure mechanism to actuate said carriage, a valve to control said flu-id pressure .y mechanism, mechanical means to .the spirit thereof,.which is set forth in the actuate said valve includingdogs orstops carried by said carriage, said means normally actuating said valve at opposite ends of the traversing movement of the carriage to procure a reversa of the carriage movement, and an additional valve to procure an extended movement of said carriage beyond the normal traverse independently of the normal actuation of the first valve by said `mecha- `2. In a grinding machine, a table or carriage vreciprocation of which causes relative traverse between grinding wheel and workpiece, duid pressure mechanism to actuate s aid carnage, a valve to control said'fluidV pressure mechanism, mechanical means to actuate said valve 'including dogs or stops carried by said carriage, said means normally actuating said valve at opposite ends of the traversing movement of the carriage to procure a reversalof the carriage movement, an Y additional valve toprocure extended move-` ment of saidcarriage beyond the normal traverse independently of the normal lactuaj tion of the first valve by said mechanism, and an additional stop on said carriage to actuate said second valve upon the extended movement of said carriage beyond normal position to reverse the direction of carriage movement, -and return said carriage to the normal reciprocatory position.

3. In a grinding machine, atable'orcarriage reciprocation of which rocuresthe grinding traverse between the grlnding wheel andV workpiece, a fluid pressure motor to actuate said carriage, a main valve to control admission .of fluid to said motor to cause the saidreciprocation, a pilot valve to actuate the main valve, pressure lines connecting one end ofsaid pilot valve to lone end of said main valve andthe other end of saidpilot valve to the other end of said main valve, and an additional valve in one of said pressure hnes to qualify the movements of said main valve vin res Y 4.

nse to movement of said pilot valve. n a grinding machine, a table or carriage reciprocation of which causes the grind-I ing traverse between the grinding wheel and workpiece, la lluidpressure motor to actuate said carriage, a' reversing valve for the Ipresthe car-l sure Huid, a 'stop valve actuated by riage in one position which cuts olf the ow Aof ii-uid to one end of said motor, and an alterliate assage for l-low of said fluid through said reversing valve to said end of grinding traverse between the grlnding wheel `and workpiece, a fluid pressure motor to actuate said carriage, and=va1ve mechamsm vto control said carriage and to stop it com' prising a valve member and a valve casing aving one port leading to one end of said motor and a pair of ports leading to the other end of said motor, a shut-of valve'associated with one of the last named ports andconnections to a source of pressure, the reversing valve being adaptedto direct the pressureeither to the first port or to the pair of ports as it is placed indifferent positions.

6. Inapparatus as`claimed in claim 5, the combination with the parts and mechanisms therein specified, of a pilot valve to actuate the said reversing/valve.

7 In apparatus of the classdescribed, a fiuid pressure., motor, a main reversing valve to control said fluid pressure motor, a: pilot valve to control saidmain reversing valve to.

reverse the flow of fluid, connections betweenv said pilot valve and said main valve, and a cut-off valve in one of said .connections to prevent shifting of said main valve in response to shifting of said pilot valve.

8. In apparatus as claimed in claim 7, the combination with the parts therein specified, of means for maintaing fluid pressure on the cut-off valve to normally hold it in position 4to allow theY fluid to fiow freely from the pilot valve to the reversing valve.

9. In apparatus'of the class described, a table or carriage, fluid pressure means to reciprocate said table or carriage, valve means to control-the said reci rocation, a throttle valve to limit the spee of reciprocation, a by-pass around the throttle valve to allow the ,speed to be increased without changing the setting of said throttle valve, and fluid pressure means to open said by-pass. c

10. In apparatus of the class described, a

'table or carriageofiuid pressure means to reciprocate said table or carriage, valve means to control the saidreciprocation, a throttle .valve to limit the speed of reciprocation, and fluid pressure actuatedmeans to render said throttle. valve ineffective to control the speed of reciprocation.

11. In apparat-us of the class described, a table or carriage, a Huid pressure motor to actuate said table or carriage, aL reversing valve to reverse the'travel of said carriage a Huid preure supply line leading to said reversing valve, a throttle valve in said fluid pressure supply line, a second fluid pressure -supply line also leading to said reversing valve, a shut-off valve normally" closed in said second fluid pressure supply line, and

lfiuid pressure means for opening said shut,- l

.- riage, reclpro'cation of whlchcauses relatlve1 off valve.

12. In a grinding machine, a table `or carriage, reciprocation'of which procures the grinding traverse between. grinding wheel and workpiece, a valve to control the speed of reciprocation of said carriage, automatic means to move said valve to restrict the fiow of fluid, saidvalve remaining in restricted position independently of the fluid flow through said valve, and fluid pressure oper ated means to reset said valve.

13. In a grinding machine, a grinding wheel, a dressing device, fluid pressure means to reciprocate said grinding wheel in relation to a workpiece, valve means to reverse said fiuid pressure means to procure a reciprocatory movement, 'fiuid pressure means to place said dressingdevice in the path of said wheel, and a single valve to operate said last -fluid pressure means and also to prevent movement of said valve means'to extend the path of travel of said grinding wheel to bring it into engagement4 with said ldressing device. l

14. In a grinding machine, a dresslng dev1ce, fluid pressure actuating means therefor,

a rotating gauge, fluid pressure means to hold said gauge out of operative position, means rgoverned by the progress of the grinding operation for rendering said first mentioned fluid pressure actuating means operative, and means actuated in response to operation of said last means to render said last mentioned fluid pressure means inoperative.

15. In a grinding machine, a dressing de vice, fluid pressure actuating means therefor, a rotating gauge, fluid pressure means to hold said gauge out of operative position, means governed by the progress of the grinding operation to admit fiuid under pressure to said first mentioned fluid pressure actuating means, and valve means actuated by said fluid under pressure to control the supply of fiuid under pressure to the secondfluid pressure means to permit said gauge to move to operative position. y

16.` In a grinding machine, a table or carriage, reciprocation of which causes relative traverse between a grinding wheel and a workpiece, fluid pressure mechanism to actu- 'ate said carriage, a main valve to control:

.said fluid pressure mechanism, a pilot valve to control the movements of said main valve,

riage, said meansnormally actuatingv said pilot valve at opposite ends of the traversingmovement of the carriage to procure a reversal ofthe carriage movement and an additional valve to procure anl lextended move ment .f of said carriage beyond the normal traversel independently oflthe normal actuation of the pilot valve by said mechanism.

1li In a grinding machine, a table or cartraverse between a grinding wheel and a workpiece, iuid pressure mechanism to actuate said carriage, a main valve to control said fluid pressure mechanism, a pilot valve 5 to control the movements of said main valve, mechanical means to actuate said pilot valve including dogs or stops carried by Lsaid carriage, said means normally actuating said pilot valve at opposite ends of the traversing movement of the carriage to procure a reversal. of the carriage movement, an additional valve to procure an vextended movement of said carriage beyond the normal traverse independently of the normal actuation of the pilot valve by said mechanism, and a valve actuated by said carriage movement to bring said carriage to rest during the extended movement.,

18, In a grinding machine, a table or carriage, reciprocation of which` causes relative traverse between a grinding wheel and. a workpiece, fluid pressure mechanism to` actuate said carriage, a main valve to control said Huid pressure mechanism, a pilot valve to control the movements bf said main valve,l mechanical means to actuate said pilot valve including dogs or stops carried by said carriage, said means normally actuating said pilot valve at opposite ends of the traversing movement of the carriage to procure a reversal of the carriage movement, an addi- 4tional valve to procure an extended movement of said carriage beyond tlienormal traverse independently of the normal actuation of the pilot valve by said mechanism, said additional valve preventing movement of the main valve in response to said pilot valve, and valve actuated in response tothe extended movement of said carriage tobring said carriage to rest, said last valve having a by-pass normally closed by said main valve during the extended movement of the carriage and opened upon shifting movement of the main valve to procure return of the carriage to normaly reciprocating positione 191,111 a grinding machine, a table or carriage, reciprocation of which causes relative traverse between a grinding wheel and ai workpiece, Huid` pressure mechanism to actuate said carriage, a main valve to control said fiuid pressure mechanism, a pilot valve to control the movements of said main valve, mechanical means to actuate said` pilot valve including dogsor stops carried by said carriage, said means normally actuating said valve at opposite ends of tbe traversing movement of the carriage to procure a reversal of the carriage movement, ean additional valve to procure an extended movement of the carriage beyond the normal traverse independently of the normal actuation of the rst valve by said mechanism, and

an additional stop on said carriage to actuate @5 said additional valve upon the extended movement of said carriage beyond normal position to reversethfe` direction of carriage movement and return said` carriage to the 

